There’s a little black spot on the sun Tuesday, but it’s not Sting’s soul, it’s Venus.

People often say something is the chance of a lifetime, but this time they are absolutely right.

Starting Tuesday afternoon in Colorado, Venus will line up between the Earth and the sun and viewers (with proper equipment) can watch the little black dot that is a planet move across the sun’s disc. This will be the last transit of Venus until 2117.

The whole event takes about six and one-half hours. Since it starts about 4:05 p.m. in Denver, it will still be going on when the sun sets here at 8:27 p.m. (Note that 4:05 will be when the edge of Venus’s dot touches the sun. It will be nearly 15 minutes until the entire little disc enters the sun’s surface.

The Associated Press has an animation that explains all this far better than I ever could, and with a far more pleasant accent.

Sorry, your browser does not support iframes

There’s also a nice explanation (and links to marvelous toys like Transit Apps for your iPhone) at transitofvenus.org

As was the case with last month’s solar eclipse, DON’T LOOK AT THE SUN! Use special solar sunglasses, shade No. 14 welder’s glass or a telescope with a solar filter.

Also, if you have a pair of binoculars, you can take the cap of one of the lenses and, without looking through the eyepiece, point it at the sun and let the image project behind you onto a light colored wall — ideally one about two or three feet away. You can watch the transit via the projection.

Safest would be to see it with the pros. Scientists Ka Chun Yu and Bob Reynolds will be in Gates Planetarium at the Denver Museum of Nature and Science starting at 5:30 p.m discussing the event with safe solar telescope viewing. ($12 for members and $15 for nonmembers, $8 for for children 3-12). Astronomers, eclipse glasses and safe telescopes will also be available at the Fiske Planetarium and Science Center in Boulder from the beginning of the transit.

The transit can also be seen at the University of Denver’s Chamberlin Observatory (via the 20-inch Clark-Saegmuller refractor) and members of the Denver Astronomical Society armed with telescopes will be gathered in Observatory Park.

Forecast Colorado is your place for the latest breaking weather news for Denver and Colorado, featuring the latest forecasts, road conditions and closures — with an occasional detour into meterological science, trivia and oddities.